1. Field of the Invention
The present invention relates a medical robotic system and a method of controlling medical robotic system and in particular, relates to a force-reflecting medical robotic system and a method of controlling the system.
2. Discussion of the Related Art
Minimally invasive surgery can reduce the amount of extraneous tissue which must be damaged during diagnostic or surgical procedures in comparison with a conventional open surgery, thereby reducing patient recovery time, discomfort, and deleterious side effects. In addition, the minimally invasive manner can minimize the trauma due to surgical procedures. Thus, the number of surgical procedures using the minimally invasive manner is gradually increasing in various medical fields such as general surgery, urology, gynecology, and cardio surgery.
However, there are also many disadvantages of current minimally invasive surgical technology. In essence, during conventional open surgeries, the tips of the various instruments may be positioned with six degrees of freedom. However, by inserting an instrument through a small aperture, such as one made in a patient to effectuate a minimally invasive procedure, two degrees of freedom are lost. It is this loss of freedom of movement within the surgical site that has substantially limited the types of minimally invasive surgery procedures that are performed.
In addition, the instruments pivot at the point (i.e. fulcrum) where they penetrate the body wall causing the tip of the instrument to move in opposite direction to the surgeon's hand.
Minimally invasive procedures are conducted by inserting surgical instruments and an endoscope through small incision in the skin of the patient. Manipulating such instruments can be awkward. It has been found that a high level of dexterity is required to accurately control the instruments. Additionally, human hands typically have at least a minimal amount of tremor. The tremor further increases the difficulty of performing minimally invasive cardiac procedures. The length and construction of instruments reduces the surgeon's ability to feel force exerted by tissues and organs on the end effector of the tool.
In order to overcome these disadvantages, techniques adapting robots to the minimally invasive surgery have been rapidly developed since 1990s. For example, teleportation techniques used in a conventional nuclear power plant and space development were utilized so as to develop these surgical robots. The system using such surgical robots enables to provide the surgeon with visual depth perception by adapting 3D stereo vision technique to a laparoscope. The system also enables to provide the surgeon with feeling as if manipulating the surgical instruments directly by his/her hand. Especially, the system enables the surgeon to perform more accurate procedures by enlarging the image while reducing the movement of the instruments.
The robotic surgery adapts coordinates transformation and position estimation techniques, like this. However, proposed methods of performing telesurgery create many new challenges. One of the challenges is transmitting force from the surgical instrument back to the surgeon's hands such that the surgeon can feel resistance to movements of the instruments when the instrument contacts tissue.
The force-reflecting control technique utilizes a Lorentz force actuator where an input current is output as a torque of a joint. This technique can be used if the status of a robot is recognized by measuring the angular velocities and the angles of the joints, and this technique embodies the force-reflection by transmitting a force to a master, which is proportional to a slave's position displacement due to a repulsive force. However, it is necessary for this technique to compensate components associated with friction, rotor inertia and structural vibration in a real motor in order to be more widely used.
Methods using a macro-micro system for overcoming such problem were developed, and these methods are disclosed in documents such as U.S. Pat. No. 5,807,377 and U.S. patent publication No. 2005/0073718 A1. The methods divide the whole system into a macro system and a micro system, thus reduce the inertia and friction of the micro system and improve the structural vibration characteristics, thereby utilize the system as a means for measuring forces. In addition, the system allows a wide range of motion of the surgical instrument by the macro system which includes multiple joints robot and also allows high positioning accuracy. The system is currently adapted to a few of the surgical robots however it is not widely used because of problems such as time delay.
Other various techniques which directly measures forces and transmit the forces to the master have been developed as another method for the force-reflecting control. These techniques may be divided into two different types, and the first type is a method for measuring torques by directly connecting torque sensors to actuators. The document, Paul, B. J., “A system approach to the torque control of a permanent magnet brushless motor,” Technical report, MIT Artificial Intelligent Laboratory, AI-TR 1081 (1987), suggested that this method can remove the effects of friction or rotor inertia. This method is disclosed in the document, Korean patent publication No. 10-2010-0075229.
The second method is to use force sensors attached at end effectors, and the document, Mason, M. and Salisbury, J. K., “Robot Hand and the Mechanics of Manipulation,” MIT Press (1985), suggested that this method can remove the effects of friction, rotor inertial and structural vibration characteristics. This method is disclosed in the document, U.S. patent publication No. 2007/0151391 A1. A method using a force/torque sensor attached at a trocar needle is also disclosed in the document, Korean patent publication No. 10-2007-0037565.
However, these methods have the following disadvantages. First, the method using torque sensors attached to actuators can induce additional position errors due to the means of measuring torque. Second, in the method using sensor attached to end effectors, it is necessary to induce a transformation of a link portion so as to increase sensitivity of the sensor, and this may deteriorate the position accuracy. The method also induces additional expenses for the surgical instruments. Third, the method using a sensor attached to a trocar needle may induce malfunction when the trocar needle is detached from the incision during the surgical procedure. Forth, the method using a sensor attached to ends of the instrument may induce problems in the expenses, sterilization and shielding EMI.
As functions of the terminal are diversified, the terminal is implemented as a multimedia player provided with composite functions such as photographing of photos or moving pictures, playback of music or moving picture files, game play, broadcast reception and the like for example.
To support and increase of the terminal functions, it may be able to consider the improvement of structural part and/or software part of the terminal.
Generally, a broadcast receiving terminal outputs a broadcast content in a manner of receiving broadcast relevant information provided by a broadcast provider and then outputting the broadcast content using the received broadcast relevant information.
In case of attempting to control a broadcast output operation, a broadcast receiving terminal receives an input of a command signal for controlling a broadcast output from a user and then performs a control operation corresponding to the inputted control command signal.
However, according to the related art, a control action for a broadcast output operation can be inputted in a manner of manipulating the broadcast receiving terminal itself. Moreover, when a control action is inputted using a small mobile terminal, a user may have difficulty in inputting the corresponding control action.